Recent reports in rhesus monkeys of successful protection against simian immunodeficiency virus (SIV) infection, using inactivated whole virus vaccines, have provided hope that a vaccine against AIDS may someday be a reality (Desrosier et al. 1989 and Murphey-Corb et al. 1989). Non-human primates infected with SIV or the human retrovirus HIV-2 represent the animal models most likely to make major contributions to the development of a successful AIDS vaccine. The objective of this proposal is to establish a SIV Vaccine Evaluation Unit (SVEU) to provide a resource to assess the safety and efficacy, partial or complete, of candidate retroviral vaccines supplied by the National Institute of Allergy and Infectious Diseases (NIAID). Mason Research Institute (MRI) will provide modern non-human primate facilities and expertise in non-human primate animal husbandry and medicine. MRI will conduct a scientific retroviral research program in the fields of virology, immunology and clinical pathology as required by the NIAID Statement of Work and any subsequent modifications. MRI perceives this as a collaborative relationship in which the MRI research team will provide facilities, services, and scientific input to conduct experiments which specifically address vaccine contract goals of the NIAID.